The present invention pertains to an axle suspension for rigid axles of vehicles, especially air-suspension, air cushioned or air sprung utility vehicles, in which a twistable, angulatable or torsionable four-point connecting rod, which is connected in an articulated manner to the vehicle axle, on the one hand, and to the vehicle body, on the other hand, and which is connected by two joints located at spaced locations from one another in the transverse direction of the vehicle to the vehicle axle and to the vehicle body, is arranged above the vehicle axle, at least one axle strut, which extends in the longitudinal direction of the vehicle and connects the vehicle axle and the vehicle body in a vertically movable manner, is arranged on each side of the vehicle for axle guidance, and at least one spring assembly unit is arranged between the vehicle axle and the vehicle body for springing or suspension.
Such axle suspensions of this type have been known from, e.g., DE 195 21 874. The design embodiment of such axle suspensions is, in principle, simple, space- and cost-saving, and has consistently proved successful in practice. However, such an axle suspension forming this type as well as other designs known from the prior art have the drawback that the axle is rigidly connected to the axle struts arranged adjacent to same. In conjunction with the entire axle construction, such a fastening leads to a kinematic overdetermination or redundancy, of the degrees of freedom of the vehicle chassis. This in turn leads to the course of the kinetic processes within the axle construction being undefined in certain situations, which may have an adverse effect on the coordination of the chassis and the chassis dynamics in the vertical and lateral directions.
Moreover, the kinematic overdetermination may lead to vibrations of the drive shaft with a resulting increase in the wear of the drive shaft and high load of the axle housing used in the case of driven axles.
The technical object of the present invention is to improve an axle suspension of this type such that the kinematic conditions are improved in order to optimize the dynamics of the vehicle movement and to achieve reduced vibrations and reduced wear as well as increased lateral rigidity of the axle construction. In addition, the number of the individual parts shall be further reduced, the ease of repair shall be increased and the unsprung or unsuspended weights shall be further reduced.
According to the present invention, the axle strut shall be connected to the vehicle axle by a molecular joint. Contrary to the axle constructions known from the prior art, the articulated mounting of the vehicle axle leads to a markedly more favorable elasticity for the entire system of the axle suspension and an unambiguous assignment or association of the kinematic conditions under all driving conditions, so that the inward and outward deflections of the axle as well as the pendular behavior are not adversely affected by squeezing, or jamming, or twisting of the vehicle axle.
It proved to be especially advantageous, in particular, that the axle struts have a mount or support for the spring assembly unit used and/or a shock absorber. The axle struts are extended for this purpose beyond the articulation point for the end connecting the axle strut to the vehicle axle at their free end not articulated to the vehicle body, and the spring assembly unit usually arranged separately between the vehicle axle and the vehicle body in prior-art constructions is accommodated at this end. The mount or support of the spring assembly unit may have a rigid or articulated design according to the present invention, and an articulated connection additionally reduces the wear of the spring assembly unit. This functional integration leads, furthermore, to a reduction in the number of components and thus to a reduction of the costs of the entire construction of the axle suspension even as a consequence of reduced assembly time and the stocking of a reduced number of parts. The spring assembly units can be optimally connected to the axle used due to the very simple axle design according to the present invention, and it is conceivable to arrange the axle struts in a V-shaped when viewed in three-dimensional space, which leads to an additional lateral stabilization. It is, of course, conceivable in this connection to provide the axle strut not only with a mount or support for one spring assembly unit, but, e.g., four or more spring assembly units, preferably air spring cushion elements in order to spring or cushion the vehicle axle.
To make it possible to adapt the kinematic conditions of the axle suspension to the design embodiment according to the present invention even better, it is, moreover, advantageous for the axle strut to be also fixed on the vehicle body by a molecular joint. This additional molecular joint should preferably have a stiffer joint characteristic than the vehicle axle-side molecular joint of the axle strut, because a cardanic angulation especially of air bellows used as spring elements is reduced hereby.
In addition, a clean design guiding of the parallelogram of both components is possible due to the spatial kinematics of the upper four-point connecting rod and of the lower axle strut with two joints, which in turn has a favorable effect on the overall kinematics of the axle and also offers the vehicle manufacturer ideal conditions for installation. In particular, the ideal trapezoid shape guiding guarantees that tie wear of the cardan universal-joint shaft is kept as low as possible.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention are illustrated.